There are many devices intended for scrubbing gaseous effluents in industry, that work mainly by adsorption of the polluting substances on adsorbing materials or by terminal separation through a filter. After scrubbing in contact with the adsorbent, the scrubbed effluents can be discharged to the atmosphere or recycled in premises at least during winter time so as to decrease heating costs.
In certain types of devices, using for example activated carbon filters working according to the principle of cohesive force and of retention by chemisorption, the adsorbents are not regeneratable and they must be replaced as soon as the saturation threshold thereof is reached. The granular activated carbon used in some other filters can be regenerated at the plant provided that it is returned to the maker. A few days of activity of the polluting plant are sometimes enough to reach this saturation threshold when the initial polluting substance concentration is high. The cost of the adsorbent or the regeneration thereof quickly becomes prohibitive. This solution of filters with non regeneratable consumables is in any case unacceptable in an ecobalance since the pollution is in this case merely transferred from one support to another without being eliminated. Because of the replacement costs, of the lack of information and sometimes of difficulties in checking the condition of the devices, it often happens that the filters are not changed as frequently as they should.
There are also scrubbing devices with adsorbent regeneration by desorption and recovery or destruction of the polluting substances. However, these devices are often more expensive. They are rather suitable for facilities generating large amounts of polluting substances. In many cases, such devices most often do not constitute economically acceptable solutions. Many facilities are therefore not adequately equipped.
U.S. Pat. No. 3,608,273 for example or patent applications FR-A-2,659,869 and FR-A-2,709,431 describe processes for treating fluids loaded with substances to be eliminated, notably consisting in passing these fluids into tanks through a series of spaced-out filter layers containing an adsorbing material such as activated carbon for example. An adsorbing material that is electrically conducting or made conducting by adding conducting particles or heating wire is used. Desorption of the adsorbate is performed by heating it by means of an electric current running therethrough or of an electro-magnetic field produced by a winding. Two arrays of filter layers may be used and one is used in adsorption while the other is regenerated.
The claimants' patent application FR-94/06,281 describes a continuous scrubbing device for polluted effluents. It includes an internally chambered ring of vertical axis loaded with a particulate solid material adsorbing the polluting substances: silica, activated carbon, alumina or others, and continuously rotating inside a cage. A permanent circulation of gaseous effluents is established on the one hand between an effluent delivery line and an exhaust line in the central area via a first angular adsorption section of the ring, and on the other hand between a hot gaseous flow delivery line in the same area and an exhaust line via a second angular desorption section of the ring, where the adsorbate is regenerated. The lines are connected to external heat exchange and/or incineration means. This device can be associated with many types of polluting plants, but it is more particularly intended for those producing relatively high rates of polluted effluents (10,000 to 100,000 m3/h for example).